Why 'Pi Day' 2016 Is Extra Special

March 14 — or 3/14 — celebrates the mathematical constant of pi. Pi represents the ratio of circumference of a circle divided by its diameter. While it is often abbreviated as 3.14, pi has an infinite number of digits beyond the decimal point, starting with 3.141592653.

Last year’s Pi Day was one to celebrate since it was 3/14/15, perfectly matching the first numbers past the decimal point of pi. Last year, hardcore math fans even started celebrating the day at exactly 9:26 a.m. and 53 seconds. There’s a big reason to celebrate this year, too — math enthusiasts are calling Monday “Rounded Pi Day.”

When rounding pi to the ten-thousandth (that’s four numbers past the decimal point), it comes out to 3.1416, matching Monday’s date — March 14, 2016.

And if you need any more reason to geek out about March 14, here’s one: it’s Albert Einstein’s 137th birthday.